1. Field of the Invention
The present invention pertains broadly to a gas flow regulator, and more particularly to a novel housing for a rotatable rotor body of a flow rate selection device.
2. Description of the Prior Art
Metering units for supplying oxygen to patients at various selected rates are well known and are in widespread use in the medical field. One type of unit employs an indexing control valve which is rotatable to a plurality of defined positions, each position providing a different rate of flow of gas to the patient. The rate of flow is determined by passing the gas from a storage tank through a selected one of an a rotary metering disk. The metering orifices are designed to, in one way or another, restrict the flow in varying amounts so that the various orifices may provide flow rates less than or on the order of 0.5, 1.0, 1.5, 2.0, 3.0 and on up to 8.0 liters per minute or more. The metering disk is rotatably mounted within a cylindrical housing or shell, and as the metering disk is rotated to selected rotary positions, only one orifice at a time may be in communication with a passage formed in the cylindrical housing. The passage is in open communication with a fitting to which a tube is coupled for supplying the gas to the patient.
In order to assure accurate flow rates over extended periods of time and to minimize the possibility of leakage of the gas, it is essential that the elements of the flow regulator be of precision construction, durable and not subject to corrosion or deterioration in the gaseous environment. To that end, the metering disk and cylindrical housing have heretofore generally been formed of a durable inert metal such as brass. Such parts require extensive machining in their fabrication and thus, while they perform very well for their intended purpose, they are relatively expensive to produce.
An additional problem associated with the well known flow regulators is the propensity of the relief mechanism to fail prematurely. This failure causes the gas to bypass the metering system and flow directly out of the pressure relief tap. The premature failure during normal operating conditions and pressures is due to the use of a rubber washer glued into a counter sunk groove in the relief valve. The washer serves as a sealing device between the relief valve and the gas inlet in the regulator housing. The failure of either the gasket or the adhesive allows the gas to flow around the relief valve and through the pressure relief tap.